I thought you were chief Android nerd, hehe.

Cryptomator allows you to create encrypted containers in the cloud (eg. Google Drive) or on local drives. It's available for all platforms. Essentially it can add an encrypted layer to storage that you don't fully trust.

I have a container setup on an external SSD, just as a way to encrypt the contents of the drive without needing something like TrueCrypt which doesn't really work AFAIK with Android.